Of Cows and Power Lines

Cattle seem to have an internal compass--one that's messed up by power lines

Posted 1 Jul 2009 | 4:00 GMT

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1 July 2009—Maybe cows are most comfortable—and willing to produce more milk—when their bodies are aligned along a north-south axis. Sound far-fetched?

A team of researchers from Germany and the Czech Republic has already discovered that, all factors being equal, cattle and two species of deer tend to align themselves along a north-south axis using some innate magnetic sense, and that this preferred alignment is disturbed when they graze under high-voltage power lines. In the next step, in their ongoing study of magnetoreception, the researchers hope to learn more about the physiological impact of magnetic fields on these and other animals.

“It could very well be that Earth’s magnetic field has an effect on physiological processes—like brain waves or blood circulation—and that this magnetic alignment could make some bodily processes function better,” says Sabine Begall, a member of the research team headed by Hynek Burda, a professor of zoology at Germany’s University of Duisburg-Essen. “We don’t know. We’re still at a very early stage in our research.”

For their research of magnetoreception and its role in spatial orientation, Burda and his team used satellite and aerial images from Google Earth to analyze cattle in open pastures. When a herd was at least 150 meters away from power lines, the researchers detected a significant alignment of the cattle along the north-south axis. By contrast, images of cattle grazing within 50 meters of high-voltage overhead power lines showed no preferred body alignment.

The researchers think they have an answer for the deviation in the east-west alignment: The alternating magnetic field produced by the power lines is perpendicular to the power lines and thus parallel to Earth’s magnetic field. The increased intensity, the researchers assume, could induce a shift in body alignment. A similar phenomenon has been observed in experiments on magnetoreceptive birds.

The magnetic sensing discovery for cattle also applies to roe deer and red deer, which the researchers observed firsthand. The team noticed that herds staying near power lines were randomly aligned and, like cows, had a greater north-south alignment when grazing beyond 150 meters of the cables.

Several species of birds, fish, and insects, as well as some small mammals, such as bats and rodents, are known to have magnetic sensing systems. Now that Burda and his team have shown that larger mammals are also able to sense magnetic fields, the researchers are curious to know why they have this capability and how they use it. Among the possible benefits magnetoreception might hold for herds of cows and deer is an ability to synchronize their direction to graze more efficiently, escape predators more effectively, or just simply feel more comfortable.

It’s not yet known how cattle feel the magnetic field. One theory focuses on magnetite crystals that magnetically receptive trout, mole rats, and pigeons have in their noses, eyes, or beaks. Another is the “radical pair” hypothesis, which involves a light-sensitive molecule called cryptochrome, used by photoreceptors in the eyes to sense blue light. Through cryptochrome, animals may actually be able to see magnetic fields as visual patterns.

In addition to physiological functions, Burda and his team plan to study magnetic alignment across diverse cattle breeds and species and the other factors that may influence it. They also want to look more closely at the possible impact of the geometry of power towers and the flow of electricity, and correlate the behavior of cattle and other animals with the actual measured values of the magnetic fields.